Table of ContentsDisadvantages of SWAPAll about Linux SWAP spaceSize used PriorityImprovementData Structure for swap on Linux systemsLinux is a free and open source operating system, it has been under active development since 1991, so the Most Linux installations suggest you include a SWAP partition. This may seem strange to Windows users who are used to having their entire operating system on a single partition. The SWAP partition acts as an overflow of your memory (RAM). If your memory is completely full, all additional applications will run from the SWAP partition in memory state. The exchange is necessary for two important reasons. First, when the system needs more memory than is physically available, the kernel replaces the least used pages and immediately gives memory to the current application (process) that needs it. Second, a significant number of pages used by an application during its startup phase may only be used for initialization and then may never be used again. The system can swap these pages and free up memory for other applications or even the disk cache. Why do we use SWAP? Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay SWAP partition works as overflowing your RAM While your memory is totally full, increase the amount of usable memory without actually getting more RAM SWAP partition can also support moving some elements of your memory. Can keep rarely needed items away from your high-speed memory. Disadvantage of SWAP Takes up space on your hard drive because SWAP partition does not change the size dynamically. Does what is necessary to improve performance.All About Linux SWAP spaceLinux has two forms of swap space: the swap partition and the swap file. The swap partition is an independent part of the hard drive used only for swapping; no other files can occupy it. The paging file is a special file in the file system that occupies between your system and data files. To see how much swap space you have, use the swapon -s command. The result will look like this: Size Used Priority Each line lists a different swap space used by the system. Now the "Type" field indicates that this swap space is a partition rather than a file, and from "File Name" we see that it is on the sda5 disk. The "Size" is listed in kilobytes and the "Used" field tells you how many kilobytes of swap space have been used, but in this example there are none. “Priority” tells Linux which swap space to use first. An advantage of the Linux swap subsystem is that if you mount two or more swap spaces (preferably on two different devices) with the same priority, Linux will interleave its swap activity between them, which can increase significantly exchange performance. To add an additional swap partition to your system, you must first provide it. The first step is to make sure the partition is marked as a swap partition and the second step is to create the swap file system. To verify that the partition is marked for swap, run as root: Fdisk -l /dev/ hdb replace /dev/hdb with the device on your system's hard drive containing the swap partition. You should see output that looks like this: Device Boot Start End Blocks Id System/dev/hdb1 2328 2434859446 82 Linux swap / Solaris. If the partition is not visible as swap, you will need to modify it by running fdisk and using the 't' menu option. Be careful when working with partitions: you don't want to delete important partitions by mistake or change your system partition ID to swap it by mistake. All data on a swap partition will be destroyed, so double-check every change you make. Also note that Solaris uses the same ID as the Linux swap space for its partitions, so be careful not to kill your Solaris partitions by mistake. At that time a partition is marked as swap, you need to prepare it using the mkswap (make swap) command as root: mkswap /dev/hdb1 If you don't see any errors, your swap space is ready to use. To start it instantly, type: swapon /dev/hdb1 You can prove it is in use by running swapon -s. To automatically mount swap space at boot time, you must add an entry to the /etc/fstab file, which contains a list of file systems and swap spaces that should be mounted at boot time. The format of each line is as follows: Since swap space is a special type of file system, many of these settings are inappropriate. For swap space, add: /dev/hdb1 none swap sw 0 0, where /dev/hdb1 is the swap partition. It has no specific mount point, now none. It is of type swap with sw options, and the last two parameters are not used so they are entered as 0. To verify that your swap space is automatically mounted without having to restart a computer, you can run swapoff - a command (which disables all swap spaces), then swapon -a (which mounts all swap spaces listed in the /etc/fstab file), then check it with swapon -s.Swap space location. Swap space can be extracted from the normal file system or into a different disk partition. A large file inside the file system: simple but inefficient. Navigating the directory structure and disk location data structure requires time and potentially additional disk accesses. External fragmentation can significantly increase swap times by forcing various lookups while reading or writing a process image. The swap space storage manager is used to allocate deallocation blocks. Use algorithms to optimize speed, instead of planning storage. The internal fragment can be increased. Linux supports both approaches. SWAP space management example: Solaris 1 Text segment pages are imported from the file system and are discarded if selected for pagination. More efficient to read back from FS than to write it to SWAP space. Swap Space: Used only as a backup store for unnamed memory pages. Solaris 2 Allocates SWAP space only when a page is moved from physical memory. Not when the virtual memory page is first created. Data Structure for Swap on Linux Systems In addition to the swap partition, Linux also supports a swap file that you can create, prepare, and mount in a manner similar to that of a swap partition. The advantage of swap files is that you don't need to find an empty partition or strip a disk to add additional swap space. To create a swap file, use the dd command to create an empty file. To create a 1 GB file, type: dd if=/dev/zero of=/swapfile bs=1024 count=1048576/swapfile is the name of the swap file and the number 1048576 is the.